Biomedical subjects
Publications and source records attributed to B D Bennett.
Quantitative ion microscopy of freeze-fractured, freeze-dried cultured cells is a technique for single cell and subcellular elemental analysis. This review describes the technique and its usefulness in determining the uptake and subcellular distribution of the boron from boron neutron capture therapy drugs.
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The natriuretic peptide receptors (NPRs) are a family of three cell surface glycoproteins, each with a single transmembrane domain. Two of these receptors, designated NPR-A and NPR-B, are membrane guanylyl cyclases that synthesize cGMP in response to hormone stimulation. The third receptor, NPR-C, has been reported to function in the metabolic clearance of ligand and in guanylyl cyclase-independent signal transduction. We engineered three chimeric proteins consisting of the natriuretic peptide receptor extracellular domains fused to the Fc portion of human IgG-gamma 1. These molecules provide material for detailed studies of the human receptor's extracellular domain structure and interaction with the three human natriuretic peptides, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and type-C natriuretic peptide (CNP). The homodimeric fusion proteins, designated A-IgG, B-IgG, and C-IgG, were secreted from Chinese hamster ovary cells and purified by protein-A affinity chromatography. We present here the primary characterization of these fusion proteins as represented by the intrinsic hormone affinities measured by saturation binding and competition assays. The dissociation constant of 125I-ANP for A-IgG was 1.6 pM and for C-IgG, 1.2 pM. The dissociation constant of 125I-Y0-CNP (CNP with addition of tyrosine at the amino terminus) for B-IgG was 23 pM. The rank order of potency in competitive binding for A-IgG was ANP greater than BNP much greater than CNP, whereas for B-IgG the ranking was CNP much greater than ANP greater than BNP. For C-IgG, we observed ANP greater than CNP greater than or equal to BNP. These data demonstrate that the receptor-IgG fusion proteins discriminate among the natriuretic peptides in the same manner as the native receptors and provide a basis for future structural studies with these molecules. The purified fusion proteins have a variety of potential applications, one of which we illustrate by a solid phase screening assay in which rabbit sera from a series of synthetic-peptide immunizations were titered for receptor reactivity and selectivity.
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We have studied the clinical utility of a recently developed assay for a prostate specific protein (prostate-specific antigen). Histochemical demonstration of prostate-specific antigen has a higher sensitivity and specificity for the diagnosis of prostate carcinoma than does prostatic acid phosphatase. Similarly, measurement of prostate-specific antigen by immunoassay in serum is a more sensitive indicator of tumor stage and recurrence after therapy than prostatic acid phosphatase. More information is needed, however, regarding the variation in this protein with different therapeutic methods.
A gene from Bacillus thuringiensis subsp. san diego that is responsible for a delta-endotoxin active against Colorado potato beetle and some other Coleoptera was sequenced and shown to have surprising regional homology with both lepidopteran and dipteran active delta-endotoxins from other strains of B. thuringiensis. Unlike the lepidopteran active toxins from B. thuringiensis subsp. kurstaki that exist as approx. 130-kDa protoxins and form bipyramidal crystalline inclusions, the coleopteran toxic protein forms a square-shaped crystal composed of an approx. 65-kDa protein. Comparisons of the gene sequences encoding the active portions of these protoxins indicate conservation of N-terminal hydrophilic and hydrophobic regions, and suggest a distant ancestral origin for these insecticidal proteins.
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Although the prostate gland is believed to serve as a parasite reservoir in trichomoniasis in men, and clinical association of trichomonads with prostatitis is common, there has been, to our knowledge, no unequivocal demonstration of Trichomonas vaginalis within the prostate gland. Using established immunoperoxidase procedures, we have positively identified trichomonads in the prostatic urethra, glandular lumina, submucosa, and stroma. Foci of nonspecific acute and chronic inflammation, as well as intraepithelial vacuolization, were associated with the infection. The finding of trichomonads within and beneath glandular epithelium necessitates reevaluation of the traditional view of T vaginalis as a strictly surface-dwelling organism.
A medical student's introduction to the clinical laboratory often sets the tone for the relationship that will exist between him or her and the laboratory throughout medical practice. As part of the sophomore pathology and laboratory medicine course at the University of South Alabama, Mobile, groups of seven or eight medical students spend one hour in each of ten different areas of the clinical laboratory. This experience acquaints the students with laboratory personnel, organization, and procedure, and emphasizes the importance of communication between clinicians and the laboratory staff. Consequently, our students have greater awareness of the capabilities and limitations of laboratory testing. This has, in turn, resulted in more efficient use of laboratory resources by clinicians and fewer complaints about laboratory service. The relatively small size of the classes in our institution enables us to schedule these sessions effectively. However, schools with larger classes could use a similar system since many of these schools have access to laboratories at more than one hospital.
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